光催化法降解农药

摘要

食品安全已经成为世界各国科学工作者重点研究的问题。农产品是食品安全中的突出对象，提高农药残留处理技术是食品安全领域广泛研究的热点。光催化氧化法能耗低，能有效地将有机污染物转化为H2O、CO2、无机离子等小分子，达到完全矿化的目的，避免了对人体健康的危害。目前国内对该技术大都还只限于实验室研究水平，且进展缓慢。本文作者采用溶胶-凝胶法成功制备了稀土掺杂改性纳米TiO2粉体，利用XRD，UV-vis等手段对样品的结构、形貌、成分和光谱特性进行了表征。得到的主要结论如下：

以钛酸正四丁酯为原料，采用溶胶-凝胶法成功制备了稀土La3+、Ce3+单掺杂及La-Fe、Ce-Fe、La-Ce共掺杂纳米TiO2粉体。粉体颗粒均匀，晶粒粒径在14~67nm范围内，随着热处理温度的升高，晶粒逐渐增大。掺杂纳米TiO2粉体颗粒均匀，掺杂纳米TiO2粉体的粒径比未掺杂纳米TiO2粉体的粒径小，说明掺杂抑制了纳米晶体的生长。

稀土离子掺杂可以抑制TiO2锐钛矿相向金红石相的转变，提高相转变温度；还可以抑制纳米晶体的生长，起到细化晶粒的作用；La3+离子的抑制能力比Ce3+离子的抑制能力强。稀土-

金属共掺杂更好地抑制了TiO2从锐钛矿相向金红石相的转变。稀土掺杂纳米TiO2的紫外-可见吸收边带位置发生红移现象。

纳米TiO氧空位2光催化剂的光催化性能在掺杂后得到明显提高，其中La3+的最佳掺杂量为0.5%，Ce3+的最佳掺杂量为1%，最佳热处理温度为500℃。稀土-金属共掺杂纳米TiO2光催化剂产生了协同效应，其光催化性能优于单掺杂样品，以La0.5%-Fe0.5%共掺杂效果最佳。

关键词溶胶-凝胶；光催化；稀土掺杂；纳米TiO2；降解农药

Abstract

Food Safety has already become a serious problems in the front of scientist around the world. Among them Agricultural products is the most severe. Improving Pesticide Residues treatment is one of the hot spots in Food Safety field. Photocatalytic oxidation method has many advantages such as it has low energy consumption, can effectively degrade some organics into H2O,CO2 and other small molecules, so it avoid secondary contamination. At present, this technology is limited in the laboratory level in China. In this

thesis, the RE doped TiO2 were prepared by sol-gel method, the structure, shape and spectrum characteristic were characterized by XRD, FE-SEM, EDS, FT-IR and UV-vis. The photocatalytic activities were evaluated by degradation of methyl orange and chloramine phosphorus. At the same time, we investigated the influence of process parameters on the fabrication of doping TiO2. Furthermore, we analyed the reaction kinetic of organics photocatalytic degradation process. The results are as follows:

Using Ti(OC4H9)4 as precursor, the La3+、Ce3+ single doped and La-Fe, Ce-Fe co-doped TiO2 were prepared by sol-gel method. The particle size of the powder is homogeneous, particle size is about 10~35nm. With the annealing temperatures increasing, the particle grown. The particle size of RE doped TiO2 is smaller than pure TiO2 ,we consider that doping restrain the growth of crystal.

The results show that the doping with optimum RE could restrain the crystal structure changing. RE doping has the effect of refining, and La3+ doping is better than Ca3+ doping. The co-doping with optimum RE and metal can restrain the transform of anatase

structure to rutile structure and the growth of crystal more effectively. FT-IR results show that Infrared absorption bands of RE doped TiO2 has been broaden, and characteristic vibration peak of Ti-O is red-shift. UV-vis results show that the absorption sideband of La3+ doped TiO2 has red-shift and widen the spectrum absorption range.

After RE doping, the photocatalytic of TiO2 has been highly improved. The optimal doping of La3+ was 0.5mol%, Ce3+ was 1mol%, and annealing temperature of 500℃. The co-doping of RE and metal show a synergistic effect for photocatalytic activity of TiO2. The co-doped TiO2 show higher photocatalytic activity in degradation of methyl orange than that of single doped TiO2. Titania co-doped with La-Fe for n(La):n(TiO2)=0.5%, n(Fe):n(TiO2)=0.05% have the highest photocatalytic efficiency.

Key words Sol-gel， Photocatalysis ，RE doping ，NanoTiO2 ，Degradation of pesticide

摘要 I

Abstract II

目录 I

第1章绪论 1

1.1 课题背景 1

1.2 半导体光催化的基本原理 1

1.2.1 TiO2的晶型及结构 1

1.3 稀土掺杂纳米TiO2的概况 2

1.3.2 掺杂TiO2光催化活性的影响因素 3

1.4 本论文研究的目的、意义及内容 5

1.4.1 研究的目的和意义 5

1.4.2 研究内容 5

（1）稀土掺杂TiO2光催化剂的制备和表征 5

第2章实验过程及方案 6

2.1 实验原料 6

2.2实验仪器与设备 6

2.3 工艺流程及控制因素 7

2.3.1 工艺流程 7

2.3.2 控制因素 7

2.4实验方案的选择 9

2.4.1、原料的选择 9

2.4.2、热处理温度的选择 10

2.4.3、降解工艺的选择 10

2.5 分析测试方法及目的 10

2.5.1光催化剂的表征 10

第3章稀土掺杂纳米TiO2光催化剂的制备及表征 12

3.1 溶胶-凝胶法制备纳米TiO2粉体 12

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